=over

=item $PREMATCH

=item $`
X<$`> X<$PREMATCH> X<${^PREMATCH}>

The string preceding whatever was matched by the last successful
pattern match, not counting any matches hidden within a BLOCK or C<eval>
enclosed by the current BLOCK.

See L</Performance issues> above for the serious performance implications
of using this variable (even once) in your code.

This variable is read-only and dynamically-scoped.

Mnemonic: C<`> often precedes a quoted string.

=back